Telephone system



C. L.GOODRUM.

TELEPHONE SYSTEM.

APPLICATION FILED APR.24, 1911.

1,362,096, v Patented Dec. 14, 1920.

2 SHEETS-SHEET 1. I 5 :3 8 r 3 b (-3. L. GOODRUM.

TELEPHONE SYSTEM.

. APPLICATION FILED APR. 24 1917. 1,362,096. Patented Dec. 14,1920.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

CHARLES L. GOODRUM, or NEW YORK, N. Y., AssIGnoE TO WESTERN ELECTRIC com- PANY, INCORPORATED, OF NEW YORK,

N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed April 24,

To all whom it may concern.

Be it known that I, CHLARLES 'L. Goon- RUM, a'citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact de scription.

This invention relates to improvements in telephone systems employing machine switching, and more particularly to systems in which telephone and telegraph messages may be transmitted simultaneously over the same conductors without inte ference.

One object of this invention is the provision of means for simultaneously controlling automatic switches and transmitting telegraph messages over the same conductors.

Another object of this invention is the provision of means for simultaneously controlling automatic switches over a phantom circuit, and transmitting telegraph messages over the metallic conductors of the physical circuits of said phantom circuit.

Another object of this invention is the provision of means whereby the release of switches used in establishing a connection between telephone lines is produced by high frequencies of current being transmitted. to said switches.

A feature of this invention is the transmission of high-frequency current over conductors to control the operation of auto matic switches to connect calling and called telephone 'lines together for conversation, while the conductors are being used to transmit telegraph-messages.

Another feature of this invention is'the provision of means in a semi-automatic telephone system whereby the removal of the calling plug by the operator transmits a highfrequency current over the trunk to disconnect the switches used in establish ing connections.

Other objects and features of this invention-will be readily understood from the following description and claims.

Referring to the drawings, Figures 1 and 2, taken together, diagrammatically repre- I Specification of Letters Patent.

Patented Dec. 14, 1920.

1917. Serial No. 164,225.

sent a telephone and a telegraph system employing thisinvention. 7

Three trunk lines T T and T are shown extending from jacks J, J andJo at-the central office B to jacks J J, and J respectively, at the central ofiice C. Two

of these trunk lines T and T are standard metallic trunk lines and are known as physical circults. In each of these physical circults, tworepeating coils, one at each central ofiice, are inserted, and leads are taken from the middle points of these coils to form a phantom circuit, which is used as the third trunk line T Thus the two line wires of each of the physical circuits are operated in parallel for the limbs of the phantom circuit. Two telegraph stations are shown connected to each line wire of each physical circuit, these stations being diagrammatically represented by a telegraph key and an impedance coil connected to battery. For simplicity only two telegraph stations 10 and 11 are diagrammatically represented. The apparatus at each of these telegraph stations, in practice, may be of any well-known type. Condensers 1, 2, 3 and 4 are inserted in each line wire and serve to keep the pulsating telegraph currents out. of the winding ofthe repeating coils. The impedance of coils 12 and 13 is very high, so that when high-frequency currents are impressed on the phy'sicalline conductors, these currents are prevented from flowing through the coils and interfering with the telegraph instruments,

whereas the low-frequency pulsating cur-. rent, produced by manually operating the telegraph keys, readily passes through these coils. Therefore, high-frequency current may be transmitted over the metallic trunk conductors without interfering with the the repeating coils R, R R, and R Since} i the telephone leads areextended from the middle of these coils, they act merely as non-inductive resistances in the phantom circuits These high-frequency currentsdo not, however, interfere with the telegraph instruments on the physical circuits, be-

cause they are unable to pass through the high impedance of the coils 12, 13, etc.

. systems, in which both metallic conductors are connected in parallel to form one telegraph circuit.

It is believed that the invention will be best understood by tracing a telephone connection from a calling subscribers substation A at the central office B to a called subscribers substation A at the central office'C.

lVhen the subscriber at substation A re- ,moves his receiver to make a call, a circuit iscompleted from grounded battery, left hand winding of relay 14, outer armature and back contact of relay 15, telephone apparatus at substation A, back contact and inner armature of relay 15, right-hand winding of relay 14 to ground. Relay 14 becomes energized and completes a circuit from grounded battery, lamp 16, front contact and armature of relay 1 1 to ground.

.The, current flowing through this circuit lights the lamp 16 in front of an operator at the central ofiice B. The operator, seeing this light, inserts plug 17 of an idle cord circuit 19 into the jack 18, associated with the calling subscribers line. A circuit is thereby completed from grounded battery, winding of relay 15, sleeve of jack 18, sleeve of plug 17 to ground. Relay 15 becomes energ zed and opens the circuit of relay 1 1, which 'denergizes and opens the circuit for lamp 16. The operator now connects her headset (not shown) to the calling subscrihers line in the well-known manner, and ascertains the number of the called subscriber. The operator then inserts the calling plug 20 of the idle cord circuit 19 into the jack J of the trunk T which extends to the central oiiice C at which the called subscrihers line termlnates. The insertion of the plug 20 into the ack J completes a cirline relay 35 of the selector switch D at the central ofiice B from the trunk T Relay 21, at its left-hand armature and front contact, completes a circuit from grounded battery, lamp 22, contact spring 23 and its nor- -mal' contact, left-hand armature and front contact of relay 21 to ground. The current flowing through this circuit lights the lamp 22 and indicates to the operator at the central oiiice B that the trunk T is in use.

A circuit is also closed at this time from grounded battery, winding of relay 2 1, front contact and armature of relay 21 to ground for a purpose hereinafter described. The operator now presses the key 26 to close its outer contacts, and then operates her impulse transmitting device 25. This impulse transmitting device may be of any wellknown type, which is arranged to close the contacts 28 a number of times corresponding to each digit of the wanted line. Each time these contacts 28 are closed, a circuit is completed from the high-frequency current generator 27, contacts 28, lower spring 26, ring conductor of the cord circuit- 19, trunk conductor 29, winding 66 of repeating coil R, trunk conductor 30, upper spring 26, tip conductor of the cord circuit 19 to generator 27. This high-frequency current flowing through the winding 66 of the repeating coil R induces a current of a similar frequency in the winding 67 of the repeating coil R, this induced current flowing over the circuit from winding 67, condenser 3, upper con ductor of trunk T condenser 1, winding 68 of repeating coil R condenser 2, lower con ductor of trunk T condenser 1, to winding 67 of repeating coil R.

Since the impedance of the coils 12, 13, etc, at each of the telegraph stations connected'to this trunk is very high, this induced high-frequency current does not affect the telegraph instruments at each of these stations. The high frequency current flowing through the winding 68 of repeating coil R induces current in the winding 69 of the repeating coil R and this current flows over the circuit from repeating coil 69, conductor 31, back contact and outer left-hand armature of relay 32, condenser 33, side-switch arm 34, winding of relay 35, side-switch arm 36, condenser 37, inner left-hand armature of relay 32, conductor 88, to winding 69 of repeating coil R Relay becomes energized each time the contacts 28 are closed, and, by attracting its armature, completes an energizing circuit for relay 39 from grounded battery, winding of relay 39, resistance 4E0, front contact and armature of relay to ground. A circuit is also closed in parallel with relay 39 from grounded bat tery, winding of relay 15, side-switch arm 17, resistances 70 and 10, front contact and armature of relay 35 to ground, but relay 4C5 does not become energized at this time due to the relatively short period of each enen gization of relay 35 and to the resistance 70 being connected in series with resistance -10, which'niakes relay 45 slow to pull up. Relay is so designed that if current is limited by the resistances 70 and 40, it i just barely sufficient to pull up the relay and the time constant of said relay will be increased sufiiciently to cause it to perform the required function. Relay 39, upon becoming energized, completes a circuit from grounded battery, winding of primary magnet 42, side-switch arm 41, front contact and ar1nature of relay 39 to ground. Magnet 42 be comes energized in response to the first closure of contacts 28 and steps the brushes 54, 55, and into operative relation with the first group of trunks. As soon as the selector switch E leaves its normal position, a circuit is completed from grounded battery, lamp 73', contact spring 72. anal its oifnormal contact to ground. The current flowing through this circuit lights the lamp 73' at the central office C, and notifies the operator thereat that the trunk T, is in use. Relay 39 also closes a circuit from grounded battery, winding of relay 43, side-switch arm 41,'front contact and armature of relay 39 to ground. Relay 43, upon attracting its armature, completes a circuit from grounded battery, winding of escape magnet 44, sideswitch arm 46, armature and front contact of relay 43 to ground. Primary magnet 42 is energized each time the contacts 28 are closed, and steps the brushes 54, 55, and 56 into operative relation with the selected group of trunks. Relay 43 is made slow to release, and, therefore, remains energized during the transmission of impulses.

At the end of the first series of impulses, the relay 39 remains deenergized since the contacts 28 are open, and thereby causes the deuergization of relay 43. Relay 43, in retracting its armature, opens the circuit of escape magnet 44, which denergizes, and moves the side switch into position 2. A circuit is then closed for secondary magnet 49 from grounded battery, winding of magnet 49, armature and back contact of magnet 49, side-switch arm 50 to ground. At the same time a circuit is completed from grounded battery, winding of escape magnet 44, side-switch arm 46 in its second position, contact spring 71 and its normal contact to ground. The secondary magnet 49 continues to operate until an idle trunk is found. The test terminals of busy trunks have battery connected thereto through the release magnet 112 of the connector switch, primary oif normal contact 150, conductor 62 to terminal 59. Therefore, as long as brush 56 engages test terminals of busy trunks similar to test terminal 59, a circuit will be completed for relay 90 from battery over the circuit just described, brush 56, winding of relay 90 to ground. Relay 90 is energized by the current flowing in this circuit, but release magnet 112 remains deenergized due to the high resistance of relay 90. Upon the first secondary step of the selector switch, the contact spring 71 engages its upper contact and escape magnet 44 remains energized until an idle trunk is found. The movement of the spring 71 is sufiiciently rapid and that of the escape magnet 44 is sufliciently slow to prevent deenergization of said magnet. Relay 90 completes at'its armature and front contact the circuit of escape magnet 44. When brush 56 engages a test terminal 59 of an idle trunk, relay 90 becomes deenergized, as its circuit is opened at primary oif-normal contact 150 of the idle connector switch. The retraction of the armature of relay 90 opens the circuit of the escape magnet which becomes deenergized and moves the side-switch wipers into position 3, the circuit for secondary magnet 49 is opened and the brushes 54, 55 and 56 are brought to rest upon terminals 57, 58 and 59 of the idle trunk. In position 3 the side-switch arms 34, 36 extend the conductors 31 and 38 to the conductors 60 and 61 of the connector switch F. In response to the second series of impulses, the line relay 100 is operated in the same manner as the line relay 35 of the selector switch E1.

Upon the first energization of relay 100,-a circuit is completed from grounded battery, winding of relay 102, resistance 103, front contact and armature of relay 100 to ground. A circuit'is also completed for relay 110 from grounded battery, winding of relay 110, resistances 111 and 103, front contact and armature of relay 100 to ground, but, due to the resistances 111 and 103 being in series, this relay does not energize at this time. Relay 102 attracts its armature and completes a circuit from grounded battery, winding of primary magnet 104,side-switch arm 105, front contact and armature of relay 102 to ground. A circuit is also completed from grounded battery, winding of relay 107, front contact and armature of relay 102 to ground. Relay 107 is made slow to release its armature, and therefore, remains energized during the transmission of this series of impulses. Relay 107 completes a circuit from grounded battery, winding of escape magnet 108, side-switch arm 109, front contact and armature of relay 107 to ground.

At the end of the second series of impulses, the relay 102 remains deenergized for a sufficient length of time to cause the detnergizaabove described, and causes the denergization of relay 107. If the called line is idle, the deenergization of relay 107 causes the escape magnet 108 to deenergize and move the side switch into position 3. In position 3, a circuit is completed for the escape magnet from grounded battery, escape magnet 108, sideswitch wiper 109 (third position), armature and back contact of relay 127 to ground. As soon as the test brush 11 6 engages contact 117 and side-switch arm 115 moves into position 3, a circuit is completed for cut-off relay 130 of the called line from grounded battery, winding of relay 130, test terminal 117, brush 116, side-switch arm 115 (third position), to ground. Relay 130 becomes energized and opens the circuit of line relay 131 of the called line, which prevents the lamp 132 from being lighted when the called party answers. In position 3, a circuit is completed from grounded battery, interrupter 126, ringing relay 127 sideswitch arm 128 (third position), brush 118, terminal 121, called substation apparatus, terminal 120, brush 119, side-switch arm 129 (third position), to ground. Ringing current is applied intermittently to the called line until the called party answers, at which time the relay 127, which is marginal, becomes energized and opens the circuit of escape magnet 108, which de'e'nergizes and moves the side switch into its fourth position. A circuit is now completed from grounded battery, left-hand winding of relay 140, sideswitch arm 129 (fourth position), brush 119, terminal 120, the called substation apparatus, terminal 121, brush 118, side-switch arm 128 (fourth position), right-hand winding of relay 140 to ground. Relay 1 10 attracts its armature and completes a circuit from grounded battery, winding of relay 141, armature and front contact of relay 1&0 to ground. The connection is now complete for the subscribers at substations A and A to carry on a conversation.

If, at the end of the conversation, the subscriber at substation A is the first to replace his receiver, relay 140 becomes deenergized and a circuit is completed for release magnet 112 of the connector switch F from grounded battery, winding of release magnet 112, armature and front contact of the slow-to release relay 1 11, armature and back contact of relay 140 to ground. Magnet 112 completes a locking circuit for itself from grounded battery, winding of magnet 112, off-normal contact 113 which was closed when the connector switch left its normal position, armature and front contact of magnet 112 to ground. The connector switch is thereby restored to its normal position, the release magnet 112 re-' maining energized until the normal position is reached, at which time the locking circuit therefor is opened at contact 113. In parallel with magnet 112, a circuit is completed for release magnet 63 of the selector switch from grounded battery, winding of magnet 63, side-switch arm 52 (third position), conductor 53, test brush 56, terminal 59, conductor 62 to ground over the previously traced circuit. Release magnet 63 becomes energized and closes a locking circuit for itself from grounded battery, winding of magnet 63, off-normal contact 51 closed when the selector switch leftits normal position, armature and front contact of magnet 63 to ground. The selector switch is thereby restored to its normal position, the release relay 63 remaining energized until the normal position is reached, at which time the locking circuit of release magnet 63 is opened at the off-normal contact 51.

If the calling subscriber had been the first to restore his receiver, a supervisory relay in the cord circuit (not shown) would have been actuated to notify the operator that the calling party has terminated the call. The operator then removes the plugs 17 and 20 from jacks 18 and J, respectively. When the plug 20 is removed from jack J, relay 21 becomes deenergized, and, by retracting its left-hand armature, completes a circuit from grounded battery, winding of relay 73, armature and front contact of relay 24, back contact and left-hand armature of relay 21 to ground. Relay 2 1 is so constructed as to keep its armature attracted an appreciable length of time after its circuit is open. Relay 73 becomes energized and attracts its armatures, which connect the high-frequency current generator 74 to the conductors 30 and 29 of trunk T This high-frequency current is repeated through the repeating coils R and R and causes the energization of relay 100. Relay 100 is maintained energized a sufficient length of time due to the relay 73 being slow to release, to allow the slow-to-pull up relay 110 to become energized. Relay 110 attracts its armature and connects ground to release magnet 112 and release magnet 63, which becomes energized and restore the switches in the manner above described.

If the called line is busy when the brushes 116, 118 and 119 engage the terminals thereof, ground is found on the test terminal 117. A circuit is then completed from grounded battery, winding of relay 11 1, armature and back contact of escape magnet 108, side-switch arm 115 (second position),brush 116, terminal 117 to ground, through a multiple test terminall17, brush 116 and side-switch arm 115 (third or fourth position) of the connector switch connected thereto. Relay 114 becomes energized and completes a locking circuit for itself from grounded battery, winding of relay 11 1, inner left-hand armature and front contact of relay 114, side-switch arm 122- to ground. Relay 114, at its right-hand armature and front contact, completes a holding circuit for escape magnet from grounded battery, winding of escape magnet 108, side-switch arm 109 (second position), armature and front contact of relay 114: to ground. The armature of the escape magnet 108 is arranged to engage its back contact before the escape magnet 108 moves the side switch into position 3. Therefore, the holding circuit "for escape magnet 108 prevents the side switchfrom moving out of position 2 into position 3. Relay 114 connects, at its outer left-hand armature and front contact, the busy back signal 125 to the line conductors 60 and 61. This busy back signal is transmitted over the trunk T to the calling subscribers substation. The calling subscriber, hearing this busy back signal, restores his receiver, which causes the supervisory relay (not shown) at the operators position, to become energized and notifies the operator that disconnection is desired. The operator then removes plug 20 from jack J, and release takes place in the same manner as above described.

If the calling subscriber had been at the central office C, and the called subscriber at the central oiiice B, selector switch D and connector switch H, at the central oflice B, would have been used. The operation would have been the same as above described. It the trunks T and T had been used, the operation would have been exactly the same except the automatic switches, associated therewith, would have been used. The highfrequency current induced in the windings of the repeating coils R and R of trunk T would have flowed through each conductor of each physical circuit in parallel, and would not, therefore, have affected any telephone or telegraph message which was being transmitted thereon.

What is claimed is:

1. In a telephone system, in combination with telegraph circuits including metallic conductors serving as line conductors for said telegraph circuits, telephone lines, automatic switches for connecting said telephone lines, and means for simultaneously transmitting over said metallic conductors one character of current for controlling the release of said automatic switches and a different character of current for the transmission of telegraph messages.

2. In a telephone system, in combination with telegraph circuits including metallic conductors, telephone lines associated with said conductors, means for connecting said telephone lines, and means for simulta-' neously transmitting over said conductors one character of current for controlling the release of said connecting means and a different character of current for the transmission of telegraph messages.

3. In a telephone system, in combination with telegraph circuits including metallic conductors, a phantom circuitfurnished by said conductors, telephone lines, means for connecting said telephone lines, and means for simultaneously transmitting over said conductors one character of current for controlling the operation of said connecting means and a different character of current for the transmisslon of telegraph messages.

4:. In a telephone system, in combination.

with telegraph circuits including metallic conductors serving asflline conductors for said telegraph circuits, telephone lines, automatic switches for connecting any-oi said lines, means for controlling the operation of said automatic switches over said metallic conductors, and means for transmitting alternating current over said metallic conductors to release said switches when one one character of current for controlling the operation of said automatic switches and a difi'erent character of current for transmitting telegraph messages.

6. In a telephone system, in combination with telegraph circuits comprising two pairs of metallic conductors, telegraph stations connected to each pair of conductors, a phantom circuit furnishedby said pair of metallic conductors, telephone lines, automatic switches for connecting any of said lines for conversation, and means for simultaneously transmitting without interference a certain character of current over said phantom circuit and over each pair of conductors for controlling the operation of said auto matic switches and a diiierent character of current over said pairs of metallic conductors between the telegraph stations for transmitting telegraph messages.

.7. In a telephone system, in combination with telegraph circuits comprising a pair of metallic conductors, telegraph stations connected to said conductors, calling and called subscribers telephone lines. means for connecting a calling subscribers line to said pair of metallic conductors, automatic switches for connecting said conductors to a called subscribers line, and means for simultaneously transmitting without interference over said conductors one character of current for controlling the release of said automatic switches and another character of current between the telegraph stations for transmitting telegraph messages.

8. In a telephone system, in combination with telegraph circuits comprising a pair of metallic conductors, telegraph stations connected to each of the pair of conductors, calling and called subscribers lines, means for connecting a calling subscribers line to said metallic conductors, automatic switches for connecting said metallic conductors to a called subscribers line, means for simultaneously controlling, over said conductors, the operation of said automatic switches and the transmission of telegraph messages between said telegraph stations, and means for transmitting alternating current over said conductors to release said switches when the first named means disconnects the said calling subscribers line from said conductors.

9. In a telephone system, in combination with telegraph circuits comprising a pair of metallic conductors, telegraph stations connected to said conductors, two telephone stations in which said pair of conductors terminates, calling and called subscribers lines terminating at said stations, means at said stations for connecting the calling subscribscribers lines to said conductors, means for connecting said conductors to the called subscribers line, means for simultaneously controlling, over said conductors, the operation of the last named meansat either of said telephone stations and the transmission of telegraph messages between said telegraph stations, and means for transmitting alternating current over said metallic conductors to release the means which connects the conductors to the called subscribers line.

10. In a telephone system, in combination with telegraph circuits comprising two pairs of metallic conductors, telegraph stations connected to each pair of conductors, a phantom circuit furnished by said pairs of conductors, two telephone stations in which said pairs of conductors and said phantom circuit terminate, telephone lines terminating at each of said stations, automatic switchesat each of said stations for connecting said pairs of conductors or said phantom circuit to said telephone lines, and means for simultaneously transmitting without interference a certain character of current over either or both pairs of conductors and over said phantom circuit for controlling the operation of the automatic switches at either of said stations and a different character of current over either of said pair of metallic conductors between the telegraph stations connected thereto for transmitting telegraph messages.

11. In an automatic telephone system, calling and called subscribers lines, an operators position, a trunk line, means at said operators position for connecting a calling subscribers line to said trunk line, automatic switches for connecting said trunk line to a called subscribers line, and means for transmitting alternating current over said trunk line to release said automatic switches when said first mentioned means disconnects said calling subscribers line from said trunk line.

12. In an automatic telephone system, calling and called subscribers lines, an operators position, a jack at said operators position, an automatic switch, a trunk line one end of which terminates in said jack and the other end of which terminates in said automatic switch, means including a plug cooperating with said jack for connecting a calling subscribers line to said trunk, means for operating said automatic switch to extend a calling subscribers line to a called subscribers line, and means for transmitting alternating current over said trunk line to release saidswitch when said plug is removed from said jack.

In witness whereof I hereunto subscribe my name this 19th day of April, A. D. 1917.

' CHARLES L. GOODRUM. 

